Method and apparatus for forming points on the ends of metal tubes



R. COPPER ETAL 3,218,836 METHOD AND APPARATUS FOR FORMING POINTS ON THE ENDS 0F METAL TUBES Nov. 23, 1965 Filed Aug. 9, 1963 4 Sheets-Sheet l //V VENTORS ROBERT L. COPPER and JAMES 1 HOUSHOLDER Attorney 3, 1965 R. COPPER ETAL 3,218,835

METHOD AND APPARATUS FOR FORMING POINTS ON THE ENDS OF METAL TUBES Filed Aug. 9. 1965 4 Sheets-Sheet 2 INVENTORS ROBERT L. COPPER and JAMES l/. HOUSHOLDER A ffarney Nov. 23, 1965 Filed Aug. 9, 1963 R L. COPPER ETAL METHOD AND APPARATUS FOR FORMING POINTS ON THE ENDS OF METAL TUBES 4 Sheets-Sheet 3 IIVVENTORS ROBERT L. COPPER and JAMES v. HOUSHOLDER Attorney Nov. 23, 1965 R. L. COPPER ETAL 3,218,836

METHOD AND APPARATUS FOR FORMING POINTS ON THE ENDS OF METAL TUBES Filed Aug. 9, 1963 4 Sheets-Sheet 4 NVE/VTORS ROBERT L. COPPER 0170' JAMES M HOUSHOLDER By Way m UFF United States Patent Ofi ice 3,218,836 Patented Nov. 23, 1965 Filed Aug. 9, 1963, Ser. No. 301,149 13 Claims. (Cl. 72-278) This invention relates to an improved method and apparatus for forming a point on the end of a tube preliminary to a cold-drawing operation.

A conventional cold-drawing operation, as applied to metal tubes, involves pulling the tube through a die which encompasses the exterior. Usually a mandrel is inserted in the tube bore to support the inside of the tube and control the size of the hole, although in a sinking operation no mandrel is used. Initially the outside diameter of the tube is larger than the die opening. Hence it is necessary beforehand to form a point on the end of the tube. The pointed end is pushed through the die opening and gripped to pull the rest of the tube through. The most common practice is to form the point in a hotforging operation, which is time-consuming and costly. Machines are known for collapsing the end of a cold tube to form a point, but such machines have not been put into extensive use. Previous machines often produce a crooked point or a bulge in the tube next to the point. Defects of this sort interfere with the drawing operation.

An object of the present invention is to provide an improved method and apparatus for forming a point on the end of a tube in which the point is formed with the tube cold after it reaches a drawbench.

A further object is to provide a drawbench and pointing machine combination which enables the pointing machine to act on tubes within the drawbench and thus eliminates extra processing and handling steps.

A further object is to provide an improved pointing machine which produces properly shaped points on cold tubes.

In the drawings:

FIGURE 1 is a top plan view of a portion of a drawbench and pointing machine combination constructed in accordance with our invention;

FIGURE 1a is a continuation of FIGURE 1 showing the remainder of the drawbench;

FIGURE 2 is a front elevational view of a portion of the combination;

FIGURE 2a is a continuation of FIGURE 2 showing the remainder of the drawbench;

FIGURE 3 is a rear elevational view of our pointing machine on a larger scale taken on line III-III of FIG- URE 1;

FIGURE 4 is an end elevational view of our pointing machine taken on line IV-IV of FIGURE 2;

FIGURE 5 is an approximately vertical sectional view of our pointing machine taken on line V-V of FIG- URE 2;

FIGURE 6 is an approximately horizontal sectional view of the die embodied in our machine taken on line VIVI of FIGURE 5;

FIGURE 7 is a diagrammatic end elevational view of FIGURE 8 is a view similar to FIGURE 7, but show ing a subsequent step; and

FIGURE 9 is an end elevational view of a tube which has a finished point formed thereon.

FIGURES 1, 1a, 2 and 2a show one form of conventional drawbench with which we can use our invention. This drawbench includes an elongated horizontal trough it a die stand 12 intermediate the length of the trough, a pair of mandrel bars 13 and 13a in the trough at the entry end of the die stand, anchor means 14 and a pushup 15 for the mandrel bars at the left end of the trough, and a carriage 16 movable along the trough at the exit end of the die stand. The anchor means 14 can shift sideways to align either mandrel bar 13 or 13a with the die stand 12. The drawbench also includes a main drive 17 for the carriage 16 located at the right end of the trough (FIGURES 1a and 20). An endless chain 18 is connected to the drive 17 and extends around an idler sprocket 19 located adjacent the die stand 12. The upper flight of the chain lies just beneath the carriage 16 and travels continuously toward the right. The carriage has a pivoted hook 20 which can be engaged with the chain to propel the carriage to the right. The carriage has jaws 21 for gripping the point at the end of a tube. The drawbench also includes suitable mechanism (not shown) for returning the carriage to its starting position at the left adjacent the die stand. A lower pinch roll 22 is mounted above the die stand and is driven by a motor 23 and transmission 24. A cooperating upper pinch roll 25 is mounted on a pivoted frame 26, which can be raised and lowered by a double-acting fluid pressure mechanism 27. A series of screws 28 are journaled in a framework 29 alongside the drawbench to receive bundles of hotrolled tubes T for cold-drawing. The screws have a drive motor 30 which can be operated as needed to move the tubes to positions where they are accessible to the operator. The screws are at progressively lower heights toward the entry end of the die stand (the left as viewed in FIGURE 2), whereby the tubes slope downwardly. The drawbench has a master control panel 31 (FIGURE 1) and the operators station is indicated at X adjacent this panel.

FIGURE 1 shows the mandrel bar 13 aligned with the die stand 12, and a tube T on this mandrel bar being drawn through the die. The other mandrel bar 13a is retracted, and initially the upper pinch roll 25 is raised. The operator lifts mandrel bar 13a to the pinch rolls, pulls another tube T down to the pinch rolls, and inserts the mandrel within the tube bore. The mandrel bars are flexibly anchored to enable bar 13a to be crossed over and above bar 13 when the latter is aligned with the die stand as shown in FIGURE 1. The operator then closes switches in the master control 31 which lower the upper pinch roll 25 and energize motor 23 to drive the lower inch roll 22 and thus propel the tube toward the left over the mandrel bar.

In conventional operation, the right end of each tube T already has a point formed thereon when the tubes arrive at the drawbench. The pinch rolls propel the tube with out interruption until the inside of the point abuts the end of the mandrel, whereupon the upper pinch roll is raised and the tube and mandrel bar 13a drop into trough 10. As soon as the preceding tube T on mandrel bar 13 clears the die stand 12, mandrel bar 13 is retracted, the anchor means 14 shifts bar 13a into alignment with the die stand, and the push-up 15 operates to push the point 3 of the tube through the die. Carriage 16 is retracted and its jaws 21 operated to grip the point. Hook 2% is engaged with chain 18 to draw the tube through the die, while the operator positions the next tube on mandrel bar 13.

In accordance with our invention, we mount a pointing machine 32 over the drawbench to the right of the die stand 12 and in alignment with the pinch rolls 22 and 25. Tubes T arrive at the drawbench without points. Our pointing machine includes a base 33 rigidly attached to the framework 29 and sloping at the same angle as the incoming tubes T. As best shown in FIGURE 5, an upright C-shaped frame 34 is rigidly fixed to base 33 and is open at the back facing screws 28 to permit each tube to enter as it travels sideways from the screws. Frame 34 carries opposed guides 35 which extend upwardly at right angles to base 33. We mount a die carriage 36 on guides 35 and a double-acting fluid pressure cylinder and piston 37 on the top of frame 34 operatively connected with the die carriage for raising and lowering it. Frame 34 also carries a stationary upstanding punch 38, and carriage 36 carries a cooperating movable die 39, the details of which are described more fully hereinafter. Both the punch and die are removably mounted, whereby they can be changed for different sizes. As best shown in FIG- URE 3, the end of the die carriage 36 remote from pinch rolls 22 and 25 carries a bracket 40 on which we mount a guide 41 and an ejector 42.. The ejector can be simply a double-acting fluid pressure cylinder and piston with a pin fixed to the end of the piston rod, and we have not shown it in detail. The end of frame 34 facing pinch rolls 22 and 25 carries a bracket 43 to which we pivot a bell crank 44. We journal a grooved idler roller 45 to one arm of the bell crank, and we connect a doubleacting fluid pressure cylinder and piston 46 between the other arm and the upper portion of frame 34. When this cylinder is operated, the bell crank turns to raise or lower roller 45. When the roller is raised, it clears tubes T to enable them to enter the back of the pointing machine. When the roller is lowered, it is positioned to engage the top of a tube engaged by pinch rolls 22 and 25.

In operation, as the operator pulls each tube T from the screws 28 to the pinch rolls 22 and 25, the tube enters the back of the pointing machine 32, where it rests on guide 41 and overlies punch 38. As the upper pinch roll 25 is lowered into engagement with the tube, roller 45 also is lowered into engagement therewith. The roller holds the tube accurately in alignment with punch 38 and die 39. As the pinch rolls retract each tube over one of the mandrel bars 13 or 13a, the tube reaches a position in which its end portion is directly over the punch. The pinch rolls are stopped with the tube in this position and act as a brake to hold the tube. Cylinder 37 is operated to lower the die carriage 36 and die 39. This action collapses the end portion of the tube to form a point thereon. Cylinder 37 again is operated, but in the opposite direction to raise the carriage and die. The ejector 42 is operated to force the pointed end portion of the tube from the die and reset. Thereafter the pinch rolls resume their movement and the operation proceeds as in the conventional practice already described.

FIGURES 6, 7 and 8 illustrate the action of our punch 38 and die 39 in more detail. The punch and die are elongated and are of a length equivalent to the length of point desired on the tube (FIGURE 6). The upper face of the punch is concave to engage the bottom of the tube (FIGURES 7 and 8). The die opening faces downwardly and has a tapered entrance portion 47 at the bottom, a straight-sided tube-flattening portion 48 extending upwardly therefrom, and a bulbous tube-expanding portion 49 at the top. The tube-expanding portion 49 tapers toward the right; the left end has a bell-shaped mouth 50 (FIGURE 6). When each tube T stops, its end portion lies immediately above the concave upper surface of punch 3 As die 39 descen t fi st flattens the tube to an oval shape as shown in FIGURE 7. Next the tube-expanding portion moves over the upper end of the oval, as shown in FIGURE 8, and effectively collapses the vertical column sections formed by the sides of the oval. Continued descent of the die folds the material inwardly and forms a point of the configuration shown in FIGURE 9. The bell mouth 50 is important as a means for preventing a bulge in the tube back of the point. A bulge would interefere with the desired processing of the tube as it passes through the die stand 12. The taper aids in releasing and ejecting the tube from the die. The point should be substantially concentric with the rest of the tube to assure that the tube is drawn in a straight line through the die stand 12. Our machine accurately aligns the tube with the punch and die to obtain the necessary concentricity. It is also essential that the point does not completely close the end of the tube. Otherwise air is entrapped between the end of the mandrel and the point and acts as a cushion on the tube. As FIGURE 9 shows, our point has the necessary opening for escape of air.

The various mechanisms embodied in our pointing machine of course can be actuated manually, but the machine is adapted for automatic actuation. When the machine operates automatically, the end of base 33 remote from pinch rolls 22 and 25 carries a bracket 51 on which we mount a flag switch 52. As best shown in FIG- URE 5, we mount an upstanding bracket 53 on base 33 and a light source 54 on said bracket. We mount a photocell 55 on frame 34 in alignment with the light source 54. The frame has an opening 56 to admit light from source 54 to the photocell. The light source is positioned below the path of tubes as they move sideways into the pointing machine in order not to interfere. As each tube enters the pointing machine, it depresses the flag switch 52, and it interrupts the light beam from the source 54 to photocell 55. As pinch rolls 22 and 25 propel the tube toward the left as viewed in FIGURES 1 and 2, the end of the tube releases the flag switch and shortly thereafter exposes photocell 55 to the light source 54. The resulting energization of the photocell signifies the tube has reached the proper positioning for pointing.

Operation of the flag switch 52 sets up a control on cuit 57 shown in block form in FIGURE 1, and energization of the photocell 55 triggers this circuit, which stops the pinch roll motor 23 and operates cylinder 37. The subsequent steps in the operation of our machine can be initiated by opening and closing of appropriate limit switches (not shown) as different operations take place. The control circuit 57 embodies conventional relays (not shown) which are energized and deenergized as the limit switches open and close. Different relay contacts in the circuit are/connected to motor 23 and to a hydraulic valve panel 58, also shown in block form in FIGURE 1. Our valve panel embodies conventional solenoid valves (not shown) and a pump 59 for operating the fluid pressure mechanisms. Both the control circuit and hydraulic valve panel operate according to well known principles, and in the interest of conciseness we have not included a detailed showing. The two fluid pressure mechanisms 27 and 46, which control the upper pinch roll 25 and the grooved roller 45, also can be interlocked to operate both at the same time.

From the foregoing description it is seen that our invention affords a simple method and mechanism for forming points on cold tubes after they reach a draw bench. The pointing operation can be automatic to the extent that the operator performs no more manual steps than he does in conventional drawbench operation. The die configuration enables the machine to point relatively heavy wall tubes with minimum hydraulic pressure. The invention is not limited to use with the particular drawbench illustrated, but can be used with drawbenches' of various other types, for example, a drawbench which has only one mandrel, or a drawbench is used in a sinking operation and has no mandrels.

While we have shown and described only a single embodiment of the invention, it is apparent that modifications may arise. Therefore, we do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

We claim:

1. In a cold-drawing operation in which metal tubes are delivered to a drawbench and each tube is pulled through a die in the drawbench to reduce its outside diameter, a method of forming points on the ends of the tubes to enable them to be started through the die comprising collapsing the end portion of each tube with the tube cold after the tubes are at the drawbench.

2. In a cold-drawing operation in which metal tubes are delivered to a drawbench and each tube is retracted to the entry end of a die and subsequently pulled in the opposite direction through the die to reduce its outside diameter, a method of forming points on the ends of the tubes to enable them to be started through the die comprising stopping each tube While partially retracted and with its end in a predetermined position, collapsing the end portion of the tube while the tube is stopped and with the tube cold, and resuming the retracting movement.

3. In a cold-drawing operation in which metal tubes are delivered to a drawbench, each tube is retracted over a mandrel bar which enters its bore, the mandrel bar pushes the end of the tube through a die, and the end of the tube is gripped at the opposite end of the die to pull the remainder of the tube therethrough, a method of forming points on the ends of the tubes to enable them to be started through the die comprising stopping each tube while partially retracted with its end in a predetermined position, collapsing the end portion of the tube while the tube is stopped and with the tube cold, and resuming the retracting movement of the tube until the inside of the collapsed portion engages the mandrel.

4. In a cold-drawing operation in which metal tubes are delivered to a drawbench, each tube is retracted over a mandrel bar which enters its bore, the mandrel bar pushes the end of the tube through a die, and the end of the tube is gripped at the opposite end of the die to pull the remainder of the tube therethrough, a method of forming points on the ends of the tubes to enable them to be started through the die comprising stopping each tube while partially retracted with its end in a predetermined position, acting on the end portion of the tube while stopped with a punch and die which collapse the end portion with the tube cold, ejecting the collapsed portion of the tube from the second-named die, and resuming the retracting movement of the tube until the inside of the collapsed portion engages the mandrel.

5. A method of cold-drawing metal tubes comprising delivering tubes without points to a drawbench, collapsing the end portion of each tube while in the drawbench to form a point thereon with the tube cold, pushing the point through a die, and gripping the point to pull the remainder of the tube through the die.

6. In a drawbench which includes means for receiving tubes, a die having entry and exit ends, means for retracting each tube from said receiving means to a position at the entry end of said die, means for thereafter pushing the tube in the opposite direction, whereby the end portion of the tube passes through said die, and means at the exit end of said die for gripping the end portion of the tube to pull the remainder of the tube through the die, the combination therewith of a machine for forming points on the ends of the tubes to enable them to be started through the die, said machine comprising means supported in alignment with said retracting means for collapsing the end portion of each tube with the tube cold after the tube leaves said receiving means and before it is fully retracted.

7. In a drawbench which includes means for receiving tubes, a die having entry and exit ends, means for retracting each tube from said receiving means to a position at the entry end of said die, means for thereafter pushing the tube in the opposite direction, whereby the end portion of the tube passes through said die, and means at the exit end of said die for gripping the end portion of the tube to pull the remainder of the tube through the die, the combination therewith of a machine for forming points on the ends of tubes to enable them to be started through the die, said machine comprising a punch and cooperating die supported in alignment with said retracting means, and means for actuating said punch and second-named die when said retracting means moves the tube to a position in which its end portion lies ,therebetween, thus collapsing the end portion of the tube with the tube cold.

8. In a drawbench which includes means for receiving tubes, a die having entry and exit ends, pinch rolls for retracting each tube from said receiving means to a position at the entry end of said die, means for thereafter pushing the tube in the opposite direction, whereby the end portion of the tube passes through said die, and means at the exit end of said die for gripping the end portion of the tube to pull the remainder of the tube through the die, the combination therewith of a machine for forming points on the ends of tubes to enable them to be started through the die, said machine comprising a punch and cooperating die, means supporting said punch and second-named die in alignment with said pinch rolls whereby a tube passes therebetween as it is retracted by the pinch rolls, and means for stopping the tube and actuating said punch and second-named die when the end portion of the tube lies therebetween, thus collapsing the end portion of the tube with the tube cold.

9. In a drawbench which includes means for receiving tubes, a die having entry and exit ends, a mandrel mounted at the entry end of said die, pinch rolls for retracting each tube from said receiving means over said mandrel, push-up means operatively connected with said mandrel for pushing the mandrel and tube toward said die, whereby the end portion of the tube passes through the die, and means at the exit end of said die for gripping the end portion of the tube to pull the remainder of the tube through the die, the combination therewith of a machine for forming points on the ends of tubes to enable them to be started through the die, said machine comprising a frame, a punch and cooperating d-ie supported on said frame in alignment with said pinch rolls, whereby a tube passes between said punch and second-named die as it is retracted by said pinch rolls, means for stopping said pinch rolls when the end portion of the tube reaches a position between said punch and second-named die, means for actuating said punch and second-named die when said pinch rolls stop, thus collapsing the end portion of the tube with the tube cold, and means for ejecting the tube from said second-named die.

10. A combination as defined in claim 9 in which said frame is open at the back to enable tubes to enter as they move sideways from said receiving means, said punch is stationary and upstanding from said frame, and said second-named die is movably supported on said frame to move up and down over said punch.

11. A combination as defined in claim 9 in which said ejecting means includes a cylinder and piston mounted on the outside of said second-named die, and comprising also a guide for tubes carried by said second-named die.

12. A combination as defined in claim 9 in which said machine further comprises a grooved roller, and means pivotally supported on said frame on which said roller is journaled, said roller having a raised position to clear tubes as they enter said frame and a lowered position aligned with said pinch rolls to engage a tube and hold it in position between said punch and second-named die.

7 8 13. A combination as defined in claim 9 in which said 1,984,756 12/1934 Offutt 205--3 machine further comprises photoelectric means supported 1,994,725 3/1935 Offutt 15348 on said frame for signifying when each tube reaches the 2,686,359 8/ 1954 Spencer 205-3 proper position for pointing. 3,068,929 12/ 1962 Rowell 15334 5 3,144,070 8/1964 Mieszcak 15334 Rtjfiiernces Cited by the Examiner FOREIGN PATENTS ED ST ATES PATENTS 816,688 10/1951 Germany. 718,671 1/1903 St1efel 2053 810,241 1/ 1906 Wikstrom 153-70 10 CHARLES W. LANHAM, Primary Examiner. 

1. IN A COLD-DRAWING OPERATION IN WHICH METAL TUBES ARE DELIVERED TO A DRAWBENCH AND EACH TUBE IS PULLED THROUGH A DIE IN THE DRAWBENCH TO REDUCE ITS OUTSIDE DIAMETER, A METHOD OF FORMING POINTS ON THE ENDS OF THE TUBES TO ENABLE THEM TO BE STARTED THROUGH THE DIE COMPRISING COLLAPSING THE END PORTION OF EACH TUBE WITH THE TUBE COLD AFTER THE TUBES ARE AT THE DRAWBENCH. 